The development of antibodies for use as human therapeutics has a long and complex history. One significant advance has been the ability to make essentially fully human antibody sequences to use in designing effective human therapeutics with reduced potential for immunogenicity. Mice now exist that are modified in their germline to generate human antibody sequences derived from unrearranged gene segments (heavy and light) either as transgenes or as replacements at endogenous mouse immunoglobulin loci. Replacement of mouse variable sequences with human variable sequences at endogenous loci in mice, as with VELOCIMMUNE® humanized mice, allow for the mouse immune system to function essentially normally. As a result, exposing these mice to an antigen of choice generates a marvelously diverse, rich population of clonally selected B cells that express high affinity somatically mutated human variable domains that can be used in making fully human antibodies directed against the antigen of choice.
Human variable domains made in humanized mice can be used to design fully human bispecific antibodies, i.e., binding proteins that are heterodimers of heavy chains, where the identities and binding specificities of the heavy chain variable domains differ. But selecting light chains that can effectively associate and express with the heavy chain heterodimers has no facile solution. Developing human light chain variable domains for use in human therapeutics is certainly possible in humanized mice, but there are no easy solutions to selecting which light chains will effectively associate and express with heavy chains having desired binding characteristics, where the light chains are not detrimental to the expression or binding behavior of both heavy chains.
Thus, there remains a need in the art for compositions and methods for developing human immunoglobulin variable regions for use in human therapeutics, including human immunoglobulin variable regions generated from nucleic acid sequences at endogenous mouse immunoglobulin loci.